Succinic acid and its derivatives are widely used as specialty chemicals with applications in foods, pharmaceuticals, and cosmetics.
Commercial fermentations for other organic acids, such as citric and lactic acids, typically produce concentrations of 80 to 120 g/l. However, such fermentations for succinic acid usually produce much lower concentrations of less than 40 g/l.
The Glassner et al. U.S. Pat. No. 5,143,834 and the Datta et al. U.S. Pat. No. 5,168,055, disclose integrated processes for the production of succinic acid employing the anaerobic bacterium, Anaerobiospirillum succiniciproducens, which produces comparatively low concentrations of succinic acid of approximately 35 g/l.
Although succinic acid is a common intermediate in the metabolic pathway of several anaerobic microorganisms, such as Propionibacterium, no microorganisms are described in the literature which produce succinate in high concentrations. Well known species of rumen bacteria convert plant carbohydrates to fatty acids and to a very large extent succinic acid.sup.(1). Prevotella ruminicola and Ruminobacter amylophilus are examples of well known species of rumen bacteria that produce major amounts of succinic acid but in generally low yields. Unfortunately, the typical rumen organisms cannot tolerate the presence of high concentrations of succinic acid or its salts and tend to lyse after comparatively short fermentation times which makes them unsuitable for industrial application. It appears that the accumulation of very high concentrations of acids, such as succinic acid, or their salts is not a normal phenomenon for microorganisms and it is damaging to them.
There is a need for a fermentation process for succinic acid which produces higher concentrations in the fermentation broth and which permit an economical recovery of succinic acid. It also would be advantageous to have microorganisms that can tolerate higher levels of succinic acid and its salts. It would be advantageous to have a method of obtaining this type of organism.